LHAASO detection of VHE gamma-ray emission from the extreme HBL 1ES 1028+511

ATel #17938; Guangman Xiang (IHEP), Min Zha (IHEP), Zhiguo Yao (IHEP), Jianeng Zhou (SHAO) and Yi Xing (SHAO) report on behalf of the LHAASO Collaboration
on 3 Aug 2026; 15:16 UT
Credential Certification: Guangman Xiang (gmxiang@ihep.ac.cn)

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We report the detection of a gamma-ray signal from the direction of the extreme high-synchrotron-peaked BL Lac object (EHBL) 1ES 1028+511 (RA = 10h31m18.5s, Dec = +50d53m36.0s) at a redshift of z = 0.361 (Polomski et al. 1997, ApJ, 486, 179). Using the LHAASO-WCDA real-time alert system, the signal was detected during the time window MJD 61251.31-61251.48 with a false alarm rate of < 0.3 events/year. A preliminary analysis indicates an observed flux of ~0.06 Crab units above 1 TeV.

1ES 1028+511 is a known VHE emitter previously detected by VERITAS and Fermi-LAT. Given the low false alarm rate, we encourage multi-wavelength follow-up observations on this source.

LHAASO is a multi-purpose Extensive Air Shower (EAS) array designed to detect air showers induced by gamma rays and cosmic rays from sub-TeV energies to above 1 PeV.